Magnesium base alloy



Patented Nov. 12, 1940 UNITED STATES MAGNESIUM BASE ALLOY John 0. McDonald, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, I a corporation of Michigan No Drawing.

Application November 13, 1939,

Serial No. 304,123

3 Claims.

The invention relates to magnesium base alloys. nature having improved physical properties.

Magnesium base alloys are finding wide use in 5 mechanical and structural arts where light weight is a desirable characteristic. In some of the uses of these alloys, such as when they are made up in extruded'forms or in rolled sheet articles, it is desirable that they possess both high 10 yield strength and tensile strength, together with sufficient ductility or formability to permit them to be formed into the desired article.

It is, therefore, the principal object of this invention to provide a magnesium base alloy having the properties of high yield and tensile strengths, together with a sufllcient degree of ductility to permit its being fabricated into cold rolled and extruded forms.

Other objects and advantages will be apparent during the course of the following description.

My invention resides in the discovery that a magnesium base alloy composed of from 0.3 to 10 per cent of silver, from 0.05 to 1.0 per cent of calcium, and from 0.3 to 10 per cent of zinc, the balance being substantially all magnesium, is endowed with the afore-mentioned properties. While the properties of high tensile and yield strengths, together with satisfactory ductility or formability, are manifest over the entire range of composition indicated, I have found that in general the preferred range of composition giving the most desirable combination of properties is found in those alloys containing from about 0.5 to 4 per cent of silver, 0.1 to 0.3 per cent of calcium, and 0.5 to 4 per cent of zinc.

The following table lists some of the properties of cold rolled sheet metal articles made from my new quaternary alloys, and compares these properties with those of the closely related parent ternary alloys having similar percentages of alloying ingredients.

It more particularly concerns alloys of this Nominal composition in percent (remainder= magnesium) Cold rolled 45 tYielgtih Tensile 3 ton strengt Zn Ag Ca in lbs./sq in lbs./sq.

in in.

The properties listed in the above table under the section headed cold rolled were obtained by subjecting specimens of the alloy, which had first been hot rolled, at a temperature from 500 to 550 F., to additional rolling in the cold state to bringabout a total reduction of from 2 to 10 per cent. The properties selected for the table were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least 1 per cent elongationin 2 inches.

By comparison of the properties listed in the above table, it will be observed that in the cold rolled state the yield strength and tensile strength of my new quaternary alloy are always superior to those of the parent ternary alloys having similar percentages of alloying ingredients. Similarly, in the higher percentage range of alloying ingredients, a corresponding improvement in properties will be noted. For example, an alloy containing 4.0 per cent silver, 4.2 per cent zinc, and 0.3 per cent calcium had a yield and tensile strength in the cold rolled state of 41,000 and 47,000 pounds per square inch, respectively. v

While the new alloy is most useful in wrought form, such as sheets, due to'its formability characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like. It is further pointed out that my new. alloy is amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

The new alloy may be compounded in any of the ways known to the art, such as by adding the alloying ingredients to molten magnesium under a suitable fiux. The flux should be substantially free from magnesium chloride if the calcium content of. the alloy is to be above 0.3 per cent. In those instances when an alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be present in the flux, but in this case it is usually desirable to add the calcium last and without too much stirring to prevent the loss of calcium into the flux.

I claim:

1. A magnesium base alloy containing from 0.3 to 10 per cent of silver, 0.05 to 1 per cent of calcium, and from 0.3 to 10 per cent of zinc, the balance being magnesium.

2. A magnesium base alloy containing from 0.5 to 4 per cent of silver, 0.1 to 0.3 per cent of calcium, and from 0.5 to 4 per cent of zinc, the balance being magnesium.

3. A magnesium base alloy consisting of approximately 3 per cent of silver, 0.2 per cent of calcium, and 3 per cent of zinc, the balance being magnesium.

JOHN C. MCDONALD. 

